The field of the disclosure relates generally to management of shared wireless communications, and more particularly, to wireless communication signal allocation in a shared unlicensed spectrum.
Conventional wireless communication systems utilize unlicensed shared spectra. For example, the 2.4 GHz, 3.5 GHz, and 5 GHz frequency bands are used with Wi-Fi, Bluetooth, Zigbee, and a range of other consumer, industrial, and medical wireless technologies. Other technology platforms also share the spectra in other frequency ranges, and available wireless spectra will become more intensively shared as demand for wireless technologies increases. In some instances, a licensed spectrum might be strictly licensed to a specified access technology, and would not be generally available to other access technologies within the same licensed spectrum.
One example of unlicensed spectrum is found in the industrial, scientific, and medical radio band (ISM band), which is a group of radio bands, or portions of the radio spectrum, that are internationally reserved for the use of radio frequency (RF) energy intended for scientific, medical and industrial requirements, rather than for communications. The ISM band extends further than merely the 2.4 GHz spectrum, but the following description is directed to operation within the 2.4 GHz spectrum for ease of explanation, and is not intended to be limiting.
RF modulation in the unlicensed 2.4 GHz ISM band generally uses techniques such as frequency-hopping spread spectrum (FHSS, or FHSS protocol) and/or direct-sequence spread spectrum (DSSS, or DSSS protocol). Bluetooth typically uses FHSS, whereas Wi-Fi typically uses DSSS, and both of these technologies operate in the 2.4 GHz ISM band. Wi-Fi technology focuses on data throughput, and the DSSS technique allows evenly-distributed channels (typically up to three) to be used simultaneously without overlapping each other. Bluetooth, on the other hand, focuses on interoperability between different communication devices, and its use of FHSS splits the 2.4 GHz ISM band into many channels (e.g., 79 channels of 1 MHz each). Bluetooth devices thus “hop” among these many channels as much as 1600 times per second in a pseudo-random pattern. Connected Bluetooth devices are grouped into networks called piconets, and each piconet typically contains one master device and up to seven active slave devices synchronized with a clock of the master.
Some conventional shared unlicensed spectrum technology systems utilize algorithm-based and sensing-based distributed access, which enable common use of a wireless resource, despite a lack of active coordination among users. For example, typical Wi-Fi systems employ a carrier sense multiple access with collision avoidance (CSMA/CA) network multiple access method, which is sometimes referred to as “listen-before-talk” (LBT), in which carrier sensing is used, but nodes attempt to avoid collisions by transmitting only when the channel is sensed to be idle (i.e., not being used). Wi-Fi devices employ a common, standards-based protocol to avoid interference among themselves and other users, which provides a substantially equal probability of access across all users in channel conditions.
Interference between Bluetooth and Wi-Fi tends to be minimal at present due to the hopping nature of the Bluetooth transmission. That is, if a Bluetooth device transmits on a frequency that overlaps the Wi-Fi channel while a Wi-Fi device is in LBT mode, the Wi-Fi device is configured to perform a random back off during which time the Bluetooth device will hop to a non-overlapping channel, thereby allowing the Wi-Fi device to begin its transmission.
However, some new technologies that are being introduced into the shared spectrum do not employ cooperative techniques. In particular, technologies utilizing Long Term Evolution (LTE), when operating in an unlicensed spectrum (LTE-U), may interfere with technologies such as Wi-Fi due to the centralized architecture of LTE and mobile systems where spectrum access is scheduled by the core network, instead of being coordinated with other access technologies accessing the same spectrum resources. Licensed-Assisted Access (LAA), which is part of the LTE-U family (also referred to as LAA LTE), specifies both contiguous and noncontiguous multi-carrier allocations, and introduction of LAA LTE has significantly increased the traffic throughput of LTE. Another LTE-based technology contemplated within the scope of this disclosure is MuLTEfire.
Present Federal Communication Commission (FCC) regulations prevent the use of Wi-Fi at the upper end of the ISM 2.4 GHz band, and specifically in the 11.5 MHz of the spectrum between 2,472 MHz and 2,483.5 MHz, due to tight out-of-band (OOB) requirements, as well as the inability of the present Wi-Fi spectral mask to comply with these FCC requirements. It would be desirable for LTE devices (including LAA, LTE-U, or MuLTEfire devices) to operate in this band since a spectral mask could be defined for the LTE devices such that the FCC OOB requirements can be met (e.g., for a carrier width of 10 MHz). However, such deployment of LTE devices would be problematic, because Bluetooth technology predominantly dominates this 11.5 MHz of spectrum because this spectral portion is essentially unoccupied at present due to the Wi-Fi limitations. Furthermore, at present there is significant resistance in the Bluetooth industry to new uses of this portion of the ISM spectrum. Accordingly, it is desirable to develop acceptable new techniques for coexistence within the ISM spectrum.